The present invention relates to a roll unit to be used in an apparatus that continuously performs electrochemical surface treatments, such as roughening treatment, rust prevention treatment and surface oxidation treatment (blackening treatment), on a surface of a rolled copper foil or an electrolytic copper foil; and in particular relates to a roll unit that can be used under a corrosion environment that generates corrosive mist.
In recent years, copper foil is being widely used in the manufacture of electronic components, wiring substrates and the like.
Generally speaking, an electrolytic copper foil is continuously manufactured by: using a rotating metal cathode drum and an insoluble metal anode (positive electrode) placed to surround roughly the lower half part of the cathode drum; electrodepositing copper on the cathode drum by flowing copper electrolyte between the cathode drum and the anode and applying a potential therebetween; and, when achieving a prescribed thickness, peeling the electrodeposited copper from the cathode drum.
In addition, the rolled copper foil is manufactured by repeatedly subjecting a melted and cast ingot to rolling and annealing multiple times.
As described above, the electrolytic copper foil and the rolled copper foil are continuously manufactured by being winded around a coil, and the obtained copper foils are used in a printed wiring board and the like after subsequently being subject to several chemical or electrochemical surface treatments.
Generally speaking, the electrochemical surface treatment of a copper foils is continuously performed by using an apparatus as shown in FIG. 1. FIG. 1 shows a lateral schematic diagram of a continuous surface treatment apparatus of a copper foil.
As shown in FIG. 1, a copper foil C winded around a coil (not shown) is continuously passed in front of opposed anodes B via several upper rolls D and a lower roll F arranged inside and outside an electrolytic tank A by being rewound, and subject to surface treatment. The surface-treated copper foil C is winded around the coil (not shown) once again. E is a guide roll. FIG. 2 shows an example of a squeeze roll unit that is attached to the continuous surface treatment apparatus. This unit comprises large-diameter rolls G corresponding to the upper rolls D of FIG. 1 and small-diameter squeeze rolls H arranged opposite thereto.
Incidentally, the squeeze roll may also be structured from stainless steel, or by using SUS304 for the shaft, steel for the cored bar of the body, and rubber lining for the outer periphery of the body.
The electrolytic tank is provided with an electrolytic solution for use in treatment such as a plating solution for roughening treatment and rust prevention treatment. The structure enables the circulation of the electrolytic solution that was replenished to or used for the initial make-up of electrolytic bath in the electrolytic tank. Current for surface treatment is flowed between the anode and the copper foil as the cathode via the electrolytic solution.
As the anode, although an insoluble anode such as a Pb plate or a noble metal oxide coated Ti plate is usually used, a soluble anode which itself melts and is electrodeposited on the copper foil may also be used. This may be changed as needed according to the conditions of the electrochemical treatment.
The width of the anode is usually decided according to the required surface treatment width of the copper foil. In the conventional electrochemical surface treatment of a copper foil described above, generally speaking, in order to prevent the solution in a former bath from getting into a subsequent bath between mutual surface treatment baths, or between a surface treatment bath and a rinsing bath, or between the foregoing baths and a winding unit, the surface-treated copper foil is passed through the squeeze roll to eliminate the solution that adhered to the surface-treated copper foil.
Solutions such as copper sulfate and chromic acid are used in the electrochemical surface treatment, and this causes a corrosion environment that is filled with gas and mist generated from the foregoing treatment solutions. With the rolls used under the foregoing circumstances, gas and mist infiltrate into the bearing, and there is a problem in that the bearing in particular is subject to severe abrasion. Thus, devices have been designed to inhibit the abrasion by filling grease into the bearing of the roll and to facilitate the replacement of the roll bearing, but such devices were insufficient.
Generally speaking, one reason that the shaft is subject to abrasion is due to the shaft abrasion that is caused by the sliding between the roll shaft and the bearing inner ring. In the foregoing case, gas and mist infiltrate the bearing of the bearing box, and it causes the bearing to corrode and results in defective rotation. Moreover, since the bearing is subject to defective rotation, sliding occurs between the roll shaft and the bearing inner ring, and the abrasion of the roll shaft, which is softer, is accelerated.
Further, although SUS304 is used as the roll shaft material for preventing the corrosion caused by gas and mist, since the reforming (hardening) of the surface of the SUS material by way of quenching is difficult, the hardness consequently becomes lower than the bearing inner ring, and it did not provide a fundamental solution.
Moreover, in the case of a structure where the oil seal and the roll shaft are in direct contact, if they are used for a long period of time, the phenomenon of the roll shaft surface being subject to abrasion on the contact surface will occur.
Moreover, since an electric field is impressed to the copper foil that comes in contact with the roll and moves during the electrochemical surface treatment, when this flows up to the roll housing (mounting frame) via a squeeze roll, there is a problem in that the copper powder will be electrodeposited on the roll, and, if the copper powder adheres to the roll, there is a problem that such copper powder will be transferred to the copper foil, whereby the quality of the copper foil will deteriorate.
When taking a squeeze roll as an example, if a standard rubber material is used in the squeeze roll, the copper powder will not be electrodeposited on the squeeze roll surface since the electrical insulation of rubber is high, but large amounts of carbon are often included in the rubber in order to improve the abrasion resistance. The reason for improving the abrasion resistance is that the squeeze roll is pressed against the upper roll at a pressure of roughly 1.2 tons, and the rubber on the roll surface is easily subject to abrasion and thereby causes adherence of rubber fragments to the copper foil surface. Large amounts of carbon are added in order to prevent the above and improve the abrasion resistance. Nevertheless, the use of a roll containing large amounts of carbon will cause a problem of considerably deteriorating the electrical insulation.
In addition, although there is a proposal of filling grease in the bearing as described above and providing an oil seal in order to inhibit the corrosion within the bearing, there was a problem in that the grease would flow to the roll main body and contaminate the roll.
In the conventional technology, a double-seal structured leakproof roll referred to as a plummer block is proposed for preventing the leakage of grease to the rolls for transporting products (refer to Patent Document 1). Nevertheless, with this kind of structure alone, it is not possible to prevent the infiltration of mist in a corrosion environment into the bearing, and it is therefore not possible to overcome the problem that the roll shaft is subject to severe abrasion.    [Patent Document 1] Japanese Patent Laid-Open Publication No. H8-159163